There is no doubt that deadly weapons being used against American forces in Iraq originated in Iran, a U.S. Forces Iraq spokesman said here today.

Maj. Gen. Jeff Buchanan led reporters traveling with Defense Secretary Leon E. Panetta on a tour of Joint Task Force Troy here, where they were free to talk to the men and women who examine all enemy ordnance to determine its origin and to look for ways to defeat the threat or prosecute those who launch attacks.

Part of the unit is the combined explosive exploitation cell laboratories.

“When (explosive ordnance disposal) teams go out and they respond to an explosive event, they collect whatever evidence they find and bring it back,” said a military official at the unit, speaking on background. “We take that evidence and take it apart and exploit it.”

The team looks at the weapon from a technical and chemical viewpoint.

“You put all those puzzles together, and you can determine where they are from,” the official said. The team also can sweep the weapons for fingerprints and DNA evidence.

Buchanan showed the reporters evidence tracing weapons used in many different attacks to Iran. One piece was an IRAM, which is short for improvised rocket-assisted mortar. The extremists took the rocket motor off a 240 mm rocket and attached a much larger warhead. They generally are shot in volleys, the general said.

Fifteen Americans were killed in Iraq in June. Nine of the dead were from just two attacks.

Reporters also saw what the military calls explosively formed penetrators, or EFPs for short. These roadside bombs can cut through the thickest and hardest armor.

“We could armor up a vehicle so an EFP charge couldn’t penetrate it, but the vehicle would be so heavy it couldn’t move,” the official said.

Neither weapon is something someone can produce on a lathe in a garage. The EFP requires very precise machining, and the explosive charge is cast. For the IRAM to be effective, it requires specially machined parts to attach the larger warhead to the missile.

The firing mechanisms are factory-made electronic parts that have no other use than firing off IRAMs or EFPs.

And the forensic teams can categorically state that the weapons are from Iran. In one case, an IRAM built in Iran was turned over to the Quds Force — part of the Iranian Revolutionary Guard — and then given to an Iraqi extremist in Kitab Hezbollah, a terrorist group that is a wholly owned subsidiary of the Quds Force, officials said.

Iran supplying munitions to the extremists alarms Gen. Lloyd J. Austin III, commander of U.S. Forces Iraq. The general said the extremists are turning to these weapons to appear as if they are driving the Americans from Iraq.

What disturbs him most is that the attacks indicate “there are folks with significant experience who are involved with trying to help develop the techniques and procedures for employing these weapons,” he said during an earlier interview.

Extremists have experimented with IRAMs since 2007.

“The two most recent attacks, we’ve seen them be a bit more effective than in the past,” he said, because the extremists are getting help from people who understand rocket science. “We’re seeing more powerful EFPs, and they seem to have matured the ability to aim these things a bit more,” the general added.

The team here is using the forensics they’ve developed to take down networks of bomb-makers. Iraqi judges are using this evidence to put the killers in jail.

When the Iraqi police or army capture the people linked to these weapons, all forensic and intelligence evidence points straight back to Iran, officials here said.